CARDIOVASCULAR REACTIONS TO EMOTIONAL STIMULI. EFFECT ON THE CARDIAC OUTPUT, ARTERIOVENOUS OXYGEN DIFFERENCE, ARTERIAL PRESSURE, AND PERIPHERAL RESISTANCE 1

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Abstract
Certain effects of anxiety on the circulation were studied in students before an examination and in hospital patients in whom anxiety was induced by suggestion. Cardiac output was measured either by the ballistocardiograph or by the Fick principle employing the technique of intracardiac catheterization. In the majority of persons, anxiety has an effect on the circulation similar to that produced by small doses of epinephrine. The cardiac output, heart rate, and O2 consumption are increased. There is a moderate elevation of blood pressure, but the peripheral resistance is decreased. The cardiac output is abnormally high in proportion to the rate of O2 consumption. When persons with this reaction undertake muscular exercise, the normal relation between cardiac output and rate of O2 consumption is re-established. In certain subjects, anxiety may be attended by circulatory collapse. In such cases, the peripheral resistance is decreased, but the compensatory increase in cardiac output fails to occur, with a resultant fall of blood pressure to low levels. In a small group of subjects, anxiety results in an increase in peripheral resistance and an elevation of blood pressure, with no change or a fall in cardiac output.